The present invention relates generally to communications systems, and, more particularly, to techniques and structures for facilitating data transmission to a receiver which is identified in a communications system by at least two different address types.
Already known by EP 0 851 703 A2 are a method and apparatus for alerting a receiver in one network about a communication request from a second network. In the case of a packet communication request, a gateway accesses a database to translate an IP address, which is associated with a mobile station as the receiver of the intended data transmission, to a subscriber identity of the mobile station. Then, the gateway requests a mobile switching centre to send an alert to the subscriber identity.
The usage of communications equipment, particularly mobile communications equipment, for transmission of data rather than speech has become increasingly popular by consumers. So-called pull services that are generally well known like Web-Browsing in the Internet, Home Banking and Electronic Shopping experience an increasing usage. Pull services have in common, that a user or a user's network initiates the individual service session set-up. E.g., a user connects via PC, laptop or mobile phone to an access server of an Internet Service Provider, to a banking computer or to an application server in order to establish the requested service session.
Also, so-called push services are increasingly demanded. Examples of such services are the generally well known News Ticker, Stock Market Information or Traffic Jam Announcements. Push services have in common, that an application server hosting the individual service application or the service application itself initiates the individual service session set-up. E.g., if a share on the stock market reaches a predefined limit, a service session can be set-up to notify a subscriber of the service.
Furthermore, it becomes more and more common to use the above described services not only via fixed networks but also via cellular communications systems like the Global System for Mobile Communication (GSM) or the Personal Digital Cellular (PDC) system. Today, such systems provide a circuit switched data service, which can be used to interconnect with external data networks. The circuit switched data service is used for both circuit switched as well as packet switched data communication.
To make packet switched data communication more efficient, new packet switched data services are introduced in cellular communications systems, like General Packet Radio Service (GPRS) as a part of GSM, or Packet Personal Digital Cellular (PPDC) as a part of PDC. Such packet switched data services will allow inter alia packet switched communications supported by a connectionless protocol like the Internet Protocol (IP). GPRS is a GSM service, and parts of the GSM infrastructure will be used. The same applies to PPDC as a PDC service, where parts of the PDC infrastructure will be used.
Usually, in today's cellular communications systems a subscriber is identified for the internal business of the system by a subscriber identity, e.g. by an International Mobile Subscriber Identity (IMSI) in GSM/GPRS and in PDC/PPDC. Inter alia, a system internal access to a subscriber profile and a locating of a subscriber is performed by use of such a subscriber identity. In contrast to this, in packet oriented communications networks that are based on the Internet Protocol (IP) both sender and receiver are identified by IP addresses. Therefore, in order to provide IP based packet switched data services cellular communications systems have to deal with two different address types, namely the IMSI and the IP address.
In the case of pull services applies a terminal originating scenario. The subscriber initialises a data session by sending a service request to a service provider, e.g. an application server, web server or bank computer. The service request is addressed by an IP address known by the subscriber that identifies the service provider. Alternatively and more convenient for the subscriber, the request can be addressed to a host name given in plain language. Then, a Domain Name Server (DNS) is used to lookup for a corresponding IP address that identifies the service provider, respectively the host. For details about the DNS, reference is made to Fred Halsall, ‘Data Communications, Computer Networks and Open Systems’, Addison-Wesley, 4th edition 1997, pp. 758, 767, 816–820.
An Internet Protocol header comprises apart from the recipient's address also the sender's address in the IP address format. This sender's IP address can be assigned either statically or dynamically in the cellular communications system. E.g., the IP address can be statically stored in a read-only memory (ROM) of the mobile terminal, or it can be assigned from a pool of addresses dynamically on demand for one data session. Therefore, in the case of the pull service scenario, the communications system knows the subscriber's IP address, particularly for a certain data session. With this knowledge, the communications system can easily transmit data packets directed to the subscriber's IP address to the subscriber that are sent during the data session from the service provider.
In the case of a push service applies a terminal terminating scenario. A solution known from the state-of-the-art for offering push services is the use of the so-called Short Message Service (SMS). E.g., today's GSM systems offer SMS as a teleservice. SMS provides a point-to-point transmission of short text messages to or from a subscriber. Furthermore, it enables short text messages to be broadcast, e.g. at regular intervals, to all subscribers in a given geographical area. On the one hand, SMS provides an easy information delivery to a subscriber. On the other hand, SMS as a bearer for push services has some limits. The amount of data that can be transmitted by a short message is limited. Furthermore, IP based packet data sessions are not supported as such. The use of a gateway that converts IP based packet data to short messages causes some overhead and additional cost.